/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.jndi;

import java.util.Hashtable;
import java.util.Properties;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NameNotFoundException;
import javax.naming.NamingException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.lang.Nullable;
import org.springframework.util.CollectionUtils;

/**
 * Helper class that simplifies JNDI operations. It provides methods to lookup and
 * bind objects, and allows implementations of the {@link JndiCallback} interface
 * to perform any operation they like with a JNDI naming context provided.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see JndiCallback
 * @see #execute
 */
public class JndiTemplate {

    protected final Log logger = LogFactory.getLog(getClass());

    @Nullable
    private Properties environment;


    /**
     * Create a new JndiTemplate instance.
     */
    public JndiTemplate() {
    }

    /**
     * Create a new JndiTemplate instance, using the given environment.
     */
    public JndiTemplate(@Nullable Properties environment) {
        this.environment = environment;
    }


    /**
     * Set the environment for the JNDI InitialContext.
     */
    public void setEnvironment(@Nullable Properties environment) {
        this.environment = environment;
    }

    /**
     * Return the environment for the JNDI InitialContext, if any.
     */
    @Nullable
    public Properties getEnvironment() {
        return this.environment;
    }


    /**
     * Execute the given JNDI context callback implementation.
     *
     * @param contextCallback JndiCallback implementation
     * @return a result object returned by the callback, or {@code null}
     * @throws NamingException thrown by the callback implementation
     * @see #createInitialContext
     */
    @Nullable
    public <T> T execute(JndiCallback<T> contextCallback) throws NamingException {
        Context ctx = getContext();
        try {
            return contextCallback.doInContext(ctx);
        } finally {
            releaseContext(ctx);
        }
    }

    /**
     * Obtain a JNDI context corresponding to this template's configuration.
     * Called by {@link #execute}; may also be called directly.
     * <p>The default implementation delegates to {@link #createInitialContext()}.
     *
     * @return the JNDI context (never {@code null})
     * @throws NamingException if context retrieval failed
     * @see #releaseContext
     */
    public Context getContext() throws NamingException {
        return createInitialContext();
    }

    /**
     * Release a JNDI context as obtained from {@link #getContext()}.
     *
     * @param ctx the JNDI context to release (may be {@code null})
     * @see #getContext
     */
    public void releaseContext(@Nullable Context ctx) {
        if (ctx != null) {
            try {
                ctx.close();
            } catch (NamingException ex) {
                logger.debug("Could not close JNDI InitialContext", ex);
            }
        }
    }

    /**
     * Create a new JNDI initial context. Invoked by {@link #getContext}.
     * <p>The default implementation use this template's environment settings.
     * Can be subclassed for custom contexts, e.g. for testing.
     *
     * @return the initial Context instance
     * @throws NamingException in case of initialization errors
     */
    protected Context createInitialContext() throws NamingException {
        Hashtable<?, ?> icEnv = null;
        Properties env = getEnvironment();
        if (env != null) {
            icEnv = new Hashtable<>(env.size());
            CollectionUtils.mergePropertiesIntoMap(env, icEnv);
        }
        return new InitialContext(icEnv);
    }


    /**
     * Look up the object with the given name in the current JNDI context.
     *
     * @param name the JNDI name of the object
     * @return object found (cannot be {@code null}; if a not so well-behaved
     * JNDI implementations returns null, a NamingException gets thrown)
     * @throws NamingException if there is no object with the given
     *                         name bound to JNDI
     */
    public Object lookup(final String name) throws NamingException {
        if (logger.isDebugEnabled()) {
            logger.debug("Looking up JNDI object with name [" + name + "]");
        }
        Object result = execute(ctx -> ctx.lookup(name));
        if (result == null) {
            throw new NameNotFoundException(
                    "JNDI object with [" + name + "] not found: JNDI implementation returned null");
        }
        return result;
    }

    /**
     * Look up the object with the given name in the current JNDI context.
     *
     * @param name         the JNDI name of the object
     * @param requiredType type the JNDI object must match. Can be an interface or
     *                     superclass of the actual class, or {@code null} for any match. For example,
     *                     if the value is {@code Object.class}, this method will succeed whatever
     *                     the class of the returned instance.
     * @return object found (cannot be {@code null}; if a not so well-behaved
     * JNDI implementations returns null, a NamingException gets thrown)
     * @throws NamingException if there is no object with the given
     *                         name bound to JNDI
     */
    @SuppressWarnings("unchecked")
    public <T> T lookup(String name, @Nullable Class<T> requiredType) throws NamingException {
        Object jndiObject = lookup(name);
        if (requiredType != null && !requiredType.isInstance(jndiObject)) {
            throw new TypeMismatchNamingException(name, requiredType, jndiObject.getClass());
        }
        return (T) jndiObject;
    }

    /**
     * Bind the given object to the current JNDI context, using the given name.
     *
     * @param name   the JNDI name of the object
     * @param object the object to bind
     * @throws NamingException thrown by JNDI, mostly name already bound
     */
    public void bind(final String name, final Object object) throws NamingException {
        if (logger.isDebugEnabled()) {
            logger.debug("Binding JNDI object with name [" + name + "]");
        }
        execute(ctx -> {
            ctx.bind(name, object);
            return null;
        });
    }

    /**
     * Rebind the given object to the current JNDI context, using the given name.
     * Overwrites any existing binding.
     *
     * @param name   the JNDI name of the object
     * @param object the object to rebind
     * @throws NamingException thrown by JNDI
     */
    public void rebind(final String name, final Object object) throws NamingException {
        if (logger.isDebugEnabled()) {
            logger.debug("Rebinding JNDI object with name [" + name + "]");
        }
        execute(ctx -> {
            ctx.rebind(name, object);
            return null;
        });
    }

    /**
     * Remove the binding for the given name from the current JNDI context.
     *
     * @param name the JNDI name of the object
     * @throws NamingException thrown by JNDI, mostly name not found
     */
    public void unbind(final String name) throws NamingException {
        if (logger.isDebugEnabled()) {
            logger.debug("Unbinding JNDI object with name [" + name + "]");
        }
        execute(ctx -> {
            ctx.unbind(name);
            return null;
        });
    }

}
